Northfield Mountain Generating Station

Northfield Mountain Generating Station

The Northfield Mountain Project ("NM Project" or "NM") is a pumped-storage facility that utilizes the Turners Falls Impoundment as its lower reservoir

The tailrace of the Northfield Mountain Project is located approximately 5.2 miles upstream of Turners Falls Dam, on the east side of the impoundment. The project includes a man-made upper reservoir situated atop Northfield Mountain, to the east of the tailrace. Water is typically pumped from the Turners Falls Impoundment to the upper reservoir at night, while generation occurs during the day.

When generating, water is passed via an underground pressure shaft to an underground powerhouse. An underground tailrace tunnel then delivers water to the Turners Falls Impoundment.

Reservoir

The crest of the upper reservoir’s main dam is at elevation 1010 feet msl. There are three dikes known as the North, Northwest, and West Dikes, and are constructed in a similar manner and to the same crest elevation as the Main Dam

Per the current FERC license for Northfield, the upper reservoir may operate between 1000.5 feet msl and 938 feet msl, which equates to a useable storage capacity of approximately 12,318 acre-feet

The upper reservoir was constructed to accommodate an elevation of 1004.5 feet msl as approved by FERC in 1976

In addition, the reservoir retains useable storage capacity down to elevation 920 feet msl. Located southwest of the upper reservoir is the intake channel that conveys water to the powerhouse

The electrical capacities of the units are as follows: Unit 1: 291.7MW, Unit 2: 291.7 MW, Unit 3: 291.7 MW and Unit 4: 291.7 MW, for a total station nameplate capacity of 1143.0 MW

Prior to efficiency improvements with the replacement of the turbine runner, and rewind of the motor-generator, the total station capacity was 1,080 MW (270 MW/unit)

When operating in a pumping mode, the approximate hydraulic capacity is 15,200 cfs (3,800 cfs/pump). Alternatively, when operating in a generation mode, the approximate hydraulic capacity is 20,000 cfs (5,000 cfs/turbine)

Water flows between the Powerhouse and the Turners Falls Impoundment via the underground Tailrace Tunnel